Tilt lens effect using Gimp

words and pictures: Peter Bargh
There's a lot of talk about tilt shift lens photography currently. The specific style of photography involves shooting with a tilt-shift lens to distort focus points and perspective, giving results that look like toy-town scenes. While doing it in camera with the necessary lens is the best way to go, digital photographers have found that Photoshop can be used. Here at ePHOTOzine we realise not everyone can afford Photoshop so we've put together a step-by-step guide showing how you can achieve a similar result using the free program Gimp.
1 Choose a suitable photo. One taken from a higher viewpoint is better as this is how you would normally view a set-up such as a model railway.

2 Open the photo in Gimp and select QuickMask mode (shortcut key Shift+Q) If your copy of Gimp does not have QuickMask download a newer version (2.6 at the time of writing).

3 Now select the Gradient tool (Shortcut key L) making sure the foreground / background colours are set to black / white (1). If you've been using different colours press key D to reset. If they are set to white / black press X to switch them.

4 Select the Bi-linear shaped gradient (2)

5 Click and hold down the mouse at a central point of the zone you would like sharp, and drag to a point where you want the gradient to end. The illustration above shows where I dragged from (circle) (point 3) to the finishing point (tip of arrow) before letting go of the mouse. This covers the areas that will be sharp in red (the mask)

6 Press Shift+Q to turn off the mask and you will notice that the areas that you want to blur (above and below the main section) now have a selection around them.

If the selection is at the wrong angle or not wide enough hit Shift-Q again and redo - the previous mask will be replaced.

7 When you're happy go to the Blur Menu: Filter>Blur>
Gimp comes with a selection of blur tools and the most effective in the standard set is Gaussian blur. You can, however, download and use the Focusblur plug-in which is more like the Lens Blur filter that Photoshop owners would use.

To do this locate the download plug-in from the Gimp site here : Focus Blur Binaries for Microsoft Windows http://registry.gimp.org/node/8236. Extract the zip file and transfer the focusblur.exe file to the Gimp plug in folder. If you did a standard Gimp install the plug-in folder .gimp-XX/plug-ins with-in your personal folder in Documents and Settings. Add this plug-in with Gimp closed and then relaunch the program for it to appear in the blur menu.

8 From Filter>Blur>Focus Blur adjust the Radius to fine tune the blur effect on the pop-up dialogue box. For this technique the only slider we need to control is the Radius which we set to 25.00. This radius softens quite heavily, but it's easy to visualise the effect and drag it to a point that looks most realistic.

9 When you're happy click ok and be prepared for a long delay as it processes and applies the effect.

10 You may then want to adjust curves to give the shot more contrast and a plasticy feel.